235 research outputs found
Numerical determination of OPE coefficients in the 3D Ising model from off-critical correlators
We propose a general method for the numerical evaluation of OPE coefficients
in three dimensional Conformal Field Theories based on the study of the
conformal perturbation of two point functions in the vicinity of the critical
point. We test our proposal in the three dimensional Ising Model, looking at
the magnetic perturbation of the , $<\sigma
(\mathbf {r})\epsilon(0)>$ and
correlators from which we extract the values of
and
. Our estimate for
agrees with those recently obtained using
conformal bootstrap methods, while , as far as
we know, is new and could be used to further constrain conformal bootstrap
analyses of the 3d Ising universality class.Comment: 4 pages, typos corrected, a few references adde
Signatures of fractional Hall quasiparticles in moments of current through an antidot
The statistics of tunneling current in a fractional quantum Hall sample with
an antidot is studied in the chiral Luttinger liquid picture of edge states. A
comparison between Fano factor and skewness is proposed in order to clearly
distinguish the charge of the carriers in both the thermal and the shot limit.
In addition, we address effects on current moments of non-universal exponents
in single-quasiparticle propagators. Positive correlations, result of
propagators behaviour, are obtained in the shot noise limit of the Fano factor,
and possible experimental consequences are outlined
Finite frequency noise for edge states at filling factor
We investigate the properties of the finite frequency noise in a quantum
point contact geometry for the fractional quantum Hall state at filling factor
. The results are obtained in the framework of the Wen's hierarchical
model.
We show that the peak structure of the colored noise allows to discriminate
among different possible excitations involved in the tunneling. In particular,
optimal values of voltage and temperature are found in order to enhance the
visibility of the peak associated with the tunneling of a 2-agglomerate, namely
an excitation with charge double of the fundamental one associated to the
single quasiparticle.Comment: 5 pages, 1 figure, to be published in the Proceedings of the
Conference on the Frontiers of Quantum and Mesoscopic Thermodynamics (FQMT11
Anomalous charge tunneling in the fractional quantum Hall edge states at filling factor \nu = 5/2
We explain effective charge anomalies recently observed for fractional
quantum Hall edge states at [M. Dolev, Y. Gross, Y. C. Chung, M.
Heiblum, V. Umansky, and D. Mahalu, Phys.Rev. B. \textbf{81}, 161303(R)
(2010)]. The experimental data of differential conductance and excess noise are
fitted, using the anti-Pfaffian model, by properly take into account
renormalizations of the Luttinger parameters induced by the coupling of the
system with an intrinsic noise. We demonstrate that a peculiar
agglomerate excitation with charge , double of the expected charge,
dominates the transport properties at low energies.Comment: 5 pages, 2 figure
Relevance of multiple-quasiparticle tunneling between edge states at \nu =p/(2np+1)
We present an explanation for the anomalous behavior in tunneling conductance
and noise through a point contact between edge states in the Jain series
, for extremely weak-backscattering and low temperatures [Y.C.
Chung, M. Heiblum, and V. Umansky, Phys. Rev. Lett. {\bf{91}}, 216804 (2003)].
We consider edge states with neutral modes propagating at finite velocity, and
we show that the activation of their dynamics causes the unexpected change in
the temperature power-law of the conductance. Even more importantly, we
demonstrate that multiple-quasiparticles tunneling at low energies becomes the
most relevant process. This result will be used to explain the experimental
data on current noise where tunneling particles have a charge that can reach
times the single quasiparticle charge. In this paper we analyze the
conductance and the shot noise to substantiate quantitatively the proposed
scenario.Comment: 4 pages, 2 figure
Charge tunneling in fractional edge channels
We explain recent experimental observations on effective charge of edge
states tunneling through a quantum point contact in the weak backscattering
regime. We focus on the behavior of the excess noise and on the effective
tunneling charge as a function of temperature and voltage. By introducing a
minimal hierarchical model different filling factors, \nu=p/(2p+1), in the Jain
sequence are treated on equal footing, in presence also of non-universal
interactions. The agreement found with the experiments for \nu=2/3 and \nu=2/5
reinforces the description of tunneling of bunching of quasiparticles at low
energies and quantitatively defines the condition under which one expects to
measure the fundamental quasiparticle charge. We propose high-order current
cumulant measurement to cross-check the validity of the above scenario and to
better clarify the peculiar temperature behavior of the effective charges
measured in the experiments.Comment: 6 pages, 3 figure
Study of the flux tube thickness in 3d LGT's by means of 2d spin models
We study the flux tube thickness in the confining phase of the (2+1)d SU(2) Lattice Gauge Theory near the deconfining phase transition. Following the Svetitsky-Yaffe conjecture, we map the problem to the study of the correlation function in the two-dimensional spin model with Z_2 global symmetry, (i.e. the 2d Ising model) in the high-temperature phase. Using the form factor approach we obtain an explicit expression for this function and from it we infer the behaviour of the flux density of the original (2+1)d LGT. Remarkably enough the result we obtain for the flux tube thickness agrees (a part from an overall normalization) with the effective string prediction for the same quantity
Integrable structures in LGTs near the deconfinement transition
In this contribution we review some recent results about the emergence of 2D
integrable systems in 3D Lattice Gauge Theories near the deconfinement
transition. We focus on some concrete examples involving the flux tube
thickness, the ratio of k-string tensions and Polyakov loops correlators in
various models.Comment: 8 pages, Poster contribution to the XXVII International Symposium on
Lattice Field Theory, July 26-31, 2009, Peking University, Beijing, Chin
Environmental induced renormalization effects in quantum Hall edge states
We propose a general mechanism for renormalization of the tunneling exponents
in edge states of the fractional quantum Hall effect. Mutual effects of the
coupling with out-of-equilibrium 1/f noise and dissipation are considered both
for the Laughlin sequence and for composite co- and counter-propagating edge
states with Abelian or non-Abelian statistics. For states with
counter-propagating modes we demonstrate the robustness of the proposed
mechanism in the so called disorder-dominated phase. Prototypes of these
states, such as \nu=2/3 and \nu=5/2, are discussed in detail and the rich
phenomenology induced by the presence of a noisy environment is presented. The
proposed mechanism justifies the strong renormalizations reported in many
experimental observations carried out at low temperatures. We show how
environmental effects could affect the relevance of the tunneling excitations,
leading to important implications in particular for the \nu=5/2 case.Comment: 14 pages, 4 figure
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